Camouflaged article and method of producing same

ABSTRACT

METHOD OF CAMOUFLAGING DYEABLE MATERIALS AGAINST DAYLIGHT OR NIGHTTIME DETECTION COMPRISING DYEING THE MATERIAL WITH A DYE COMPOSITION PRODUCING A DESIRED SHADE IN THE VISIBLE RANGE OF THE SPECTRUM AND FLUORESCENCE IN THE NEAR INFRARED RANGE FROM 0.70 TO 0.90 MICRON WAVELENGTH, AND OVER-PRINTING THE DYED MATERIAL WITH LINES OF A PRINTING COMPOSITION CONTAINING AN ENERGY ABSORBENT PIGMENT, SUCH AS CARBON; AND CAMOUFLAGED ARTICLES PRODUCED BY THE METHOD.

uw' .my nu@ v Aro. RAMSLEY ETAL 3,700,397

UAMOUFLAGFD ARTICLE AND METHOD OP PRODUFTNG SMH.

mcd Mumia, 1959 o o (D .Y L0

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Oct. '124,I 1972 A. O. RAMSLEY Er AL 3,700,397

CAMOUFLAGED ARTICLE AND METEO!) Ol-` 1EODUQ1NG SAME H AFaled May 6, 1969 1 2 Sheets-Sheet 2 O qu O O no un HOLQVd NOILOBHBH o.. @o @o No wd @o m o W 1w I||l\m o. m ow n xulm w Dz 10.35 210@ 2 .www w i .qo @www im whim@ J u L o@ MM m MM i 0mm www y O@ M w mrw @5.0mm l/ o mw@ om States Patent ,t 3,700,307 CAMOUFLAGI'I) AR'llCLlt ANI) Ml'l'llUl) 0l" i' PRODUCING SAME Alvin 0. Ramsley, Sherhorn, and .lohn 'l`. Walwootl, Lowell, Mass., assignors to the United States of America as represented by the Secretary of the Army Filed May, 1969, Ser. No. 822,218

Int. Cl. D06p 3/00; F41h 3/00 l ABSTRACT OF TIXIHF, DISCLOSURE Method of camoufluging dyeable materials against daylig-ht or nighttime detection comprising dyeing tht` ninterial with a dye composition producing a desired shade in the visible range of the spectrum and fluorescence in the near infrared range lfrom 0.70 to 0.90 micron wavelength, and over-printing the dyed material with lines of a printing composition containing an energy absorbent pigment, such as carbon; and camouflaged articles producedl by the method. i ,is

The invention described herein may be manufactured, used, and licensed `by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to a camouflagcd article and a method of producing the same. More particularly, the invention relates to eamouflaged fabrics and camouflagcd articles produced therefrom..

ln the conduction of military field operations the camouflaging of the uniforms of soliders and of their shelters and other equipment has become very important to prevent detection thereof in the daytime by visual observation or by aerial photography employing infraredsensitive photographic film which is particularly sensitive in the wavelength range of the spectrum from about 0.70 to about 0.90 micron and at'night by electro-optical means, such as the so-called sniperscope, which usually employs radiations in the wavelength range of the spectrum from about 0.90 to about 1.20 microns.

Heretoforc, camouflaging of military uniforms and other military equipment has been carried out primarily With respect to light in the visible range of wavelengths, generally from about 0.38 to about 0.70 micron. This has been done by dyeing or pigmenting fabrics and other materials with varicolored designs to simulate and blend with the surroundings in which the articles made of such fabrics or other materials are to be used, for example,

jungle surroundings, rock formations, or other special situations. However, inasmuch as other methods of detection, such as aerial photography, employing;radiations in` the` infrared region of the spectrum haflxg' beed' dcveloped in recent years to supplement visual observation, conventional methods of camouflaging have become relatively ineffective. i

Methods have been developed for dyeing fabrics or other dyeable materials with dyes which fluoresce strongly in the near infrared region of the spectrum, particularly at wavelengths from about 0.70 to about 0.90 micron.

Such dyed materials blend well with backgrounds freV ouently encountered by the military forces, such as grass or earth. Materials dyed with such dyes do not show up in aerial photographs nearly so distinctly as materials dyed withv conventional dyes, such as the olive green dyes. that have been standard for military uniforms and other equipment for many years. However, these dyes generally have the disadvantage that they also reflect to a high degree in the wavelength range from about 0.90 t about 1.20 microns employed in electro-optical methods ice of detection such as `the snipcrscope. llencc. uniforms and other articles dyed with dyes that flnorcscr` in thc` near infrared range are usually easily detected by menus ofthe sniperscope at night. Separate uniforms for daytime und nighttime use could be issued to overcome this dilemma; but this would crczac a very severe logistic problem as well as greatly increased costs. It is, therefore, highly' desirablerlo have a method cf obtaining effective camouflage against detection by visu-al observation in the wavelength range from about 0.38 to about 0.70 micron, but at the same time providing in the same article effec* tive camouflage against detection by aerial photography using film sensitive in thc wavelength range from about 0.70 to about 0.00 micron and against detection by a sniperscope employing wavelengths in the range from about 0.90 to about 1.20 microns-or even higher.

An object of the invention is to provide a method of obtaining effective camouflage of an article over the wavelength range of the electromagnetic spectrum from about 0.38 to about 1.20 microns.

A further object of the invention is to provide articles effectively camouflagcd. against detection by visual observation employing radiation in the wavelength range from about 0.38 to about 0.70 micron and by photographic and electro-optie methods employing radiation in tho wavelength range from about 0.70 to about 1.20 microns, or higher.

Other objects and advantages will appear from the description of the invention hereinafter and the accompanying drawings wherein:

FIG. l is a graph of the reflection factor at various wavelengths of fight for fabrics dyed and printed in accordance with Example l hereinafter.

llG. 2 is a graph of the reflection factor at various wavelengths of fight for fabrics dyed and printed in accordance with Example 2 hereinafter.

FIG. 3 is a plan ,view of a fabric dyed and printed in accordance withI Example 2.

FIG. 4 is a graph of the reflection factor atl various wavelengths of lightfor fabrics dyed and printed in accordance with Example 3 hereinafter.

FIG. 5 is a graph of the reflection factor at various wavelengths of light for fabrics first printed and subsequently dyed in accordance with Example 4 hereinafter.

The objects of the invention are accomplished in one embodiment of the invention by dyeing a fabric with a dye, or a mixture of dyes, which produces a fluorescent dyed surface on the fabric having a high reflection factor in the infrared wavelength raii'ge of the electromagnetic spectrum from about 0.70 to about 0.90 micron, drying the dyed fabric, printing the surface of the dyed fabric in a substantially uniformly distributed pattern, such as spaced lines, using a printing Vcomposition which is highly energy absorbent in the entire wavelength range involved, i.e. 0.38 to 1.20 microns, and drying the printed fabric. The dye is selected for the particular type of fabric and the printing composition is printed on the dyed fabric in such a pattern that the dyed and printed fabric has reflection factors of less than about 35% for radiant energy in the wavelength ranges from about 0.38 t0 4about 0.70 micron and from about 0.90 to about 1.20

microns and a reflection factor for radiant energy of at least one,wavelength in the 'Wavelength range of from about 0.70 to about 0.90 micron which is not less than about 35%. l

As will be readily apparent from an examination of the drawings, the reflection characteristics curves of materials embodying the invention include a distinct peak reflection factor in the wavelength range of from about 0.70 to about 0.90 micron. The occurrence of this peak is essential to the `ltiilectiveness of the material as camouflage against infrared photography and, while it is desirable that the peak be substantially higher than the portions of the curves in the. lower and higher vuvelength ranges. thead'vauttnxes of tite invcntitin are reali/.ed so iongas the peak equals or exceeds 35% at sortie wavelength within the 0.70 lo 0.90 micron range while the rcflei'ction factors in the i-ower and higher wavelength ranges hre maintained below the 35% level, we have found that reflection factors in thet).70 to 0.90 micron wavelength range which are at least f0% greater than the reflection factors in the lower' andihigher wavelength ranges are readily obtainable in accordance with the present invention as evidenced by FIGS. l. 2. 4 and 5.

The objects may also be attxilined by first printing spaced lines on the` surface of the-'fabric` usine` the black pigluem-containing highly energy `tbsorbent resin emulsion printing composition. drying the printed lines. liteit as aforementioned` thereby dyeing the fabric bct\\ccn the printed lines and obtaining a printed and dyed fabric having substantially the same light reflection characteristics as the above-described fabric which is 'first dyed and then printed with the black pigment-containing lines.

As a result of either of the above-described dycinggand printing or printing and dyeing" procedures, -a product is obtained which has` reflection factors below about 35 percent in the visible range of the spectrum. i.e. at \vave lengths of from about 0.38 to about 0.7.0 micron, a reflection factor not less than about 35 percent in at least one wavelength of the near infrared range of the spectrum,'i.c. from about 0.70 to about 0,90 micron, and reflection factors below about 35 percent in the far infrared range of the spectrum, i.e. at wavelengths above about V0.90 micron and particularly between about 0.90 to about 1.20 microns. The net effect is that the retlection factor curve for-the product, which is determined with Beckman DU Spcctrophoton'ictcr, is appreeiabiy altered so that the product has lower reflection factors over the Iwavelength range of,l thel spectrum from about 0.38'micron to about 1.20 microns` but retains effectively high rellectionffactors over the near infrared wavelength range from about 0.70 to about 0.90 micron. Thus, the product blends in well with backgrounds which lluoresce or reflect well in the near infrared range of the spectrum and is, therefore, effectively camoufiaged against aerial photography, while not iluorescing or reflecting -very strongly in the far infrared wavelength range above 0.90 micron and, therefore, being effectively camouilagcd against detection by means of the'sniperscope at night using wavclengthsrin the range from about 0.90 to about 1.20 microns. The material is also effectively camoullaged n against visual observation by daylight or artificial light l`in=the visiblerange when observed beyond certain drstanees, the printed lines blending in with the dye'd portions of fabric bet-Ween the printed lines at or beyond such distances. If, for example, the dye composition is selected to produce an'olive drab color, then therjiroduet-l wii'l blend well with all backgrounds with wfyibh the olive drab color normally blends despite the presence of the black pigment-containing lines,'and beyond the selected distance for visual observation of the product. The overall result, therefore, is that the product is 'effectively camouflaged against detection during the daytime and nighttime over the spectral range from about 0.38 micron to about 1.20 microns or even higher wavelengths, provided the point of observation is more than a preselected 'distance from theproduct. The 'wider the printed lines are and the fartherapart they are on the dyed background of the product, the farther away the point of observation of the product must be in orderfor it to be camouffaged. It is impractical in general to print lines narrower than about one-sixteenth inclr wide separated -about one-sixteenth inch apart on fabrics, although on other types of dyeing the printed fabric with n d ve. or mixture of tives.

Ill)

. 4 products. for example films. paper and the like. narrower lines and separations of the printed lines may bc cmpioyed in order to reduce the distance from which observation mn \fl be carried otlt without a clear-cut detection ttl. tilt` lttUdlltf.

i-`or the purposes of this application, the near infrared is defined as thc range of wavelengths ofl the electromagnetic spectrum between about (1.7() and 0.90 micron, and the fur infrared is defined as tht` range of' wavelengths ol' the electromagnetic sp'y :lrunt between about 0.90 and about 1.2() microns, or higher. The visible wavelength rangeY is generally from about 0.78 to about 0.70 micron.

Also. for the purposes of this application, the reflection factor is defined as thc sum of the normal reflection plus the contribution of fluorescence at a given wavelength of thc.electromagnetic spectrum hen a specnneu is illu-- miuatcd by white light produced by a -xenon lamp. 'lhe reflection factor is c\pressed in terms of percent of the light emerging from the surface compared with that which would be reflected by magnesium oxide at the given wavelength` using a Beekman DU Quartz Spectrophotometcr for analyzing the light emerging from the respective surfaces at the various wavelengths of interest.

For the purposes of the present invention, Table l lists a number of dyes which have been found-to iluorescc strongly in the near infrared range of the spectrum and are useful either alone or in combination with other dyes for obtaining the desired color effect in the visible range of the spectrum as well as fluorescence in the infrared. Table 1 also indicates the type of substrate material in the form of fabric with which cach dye has been found Yto be particularly effective in terms of fluorescence in the 'IAilLiE 1 iCollar nt ex Ty )o of'y Dye number Chemical type sulistrate Basie Blue 3 51005 n flasie Blue-l 5100i Pohl'iiyhc Basie llillt` 7 425515 Do. Basic Blue 'l 52012' l`hiazine D0. Basie Blue 1 51i.\`0 Oxazine Do. Baste Blue .1G 44015 Triaryimethane Do. Basie Bine 3 None .do Do. Azure A 52005 flhiazine Do. Baste Green 1` /fltltO l`riarylntefhane Do. Basie Green 3- None do Do. Basle Green-5. Do. Basie Violet 3. Do. Basie Violet -l Do. Basie Violet 5. 50205 Azine D0. Aeld Bitte 1 4201.5 '1riarylmutnane Polyamide. Arid Blue 3... do Do. Acid Bitte 7... Do. Acid Blue fl... do D0. Acid Blue 63 None-1 Anthranunone. lo. Acid Green. .t Do.

.l lio. Acid Green 16 41025 Aetd Green 22 21H0 Direct Blue 3 23705 t Directr Bine 8 211.10 .Directy liiltu il .llrtt'itl Direct lline, 15 24100 Direct Blue 2t 237|!) Direct. Bine 22 '24280 Direct illne 23 21405 Direct Blue 25 23700 mrtwt num 27 '2.17m Direct iiitte 53 12380() 110 Direct lilne `(il None Direct lllun 10... 51300 llireefl flirte 107. 51315 Direct. lllue 10S. 515420 Direct. iiun l0' lill) Dirt-.nl Blue. ltitL None .o lio. Dlspersn illue EL ttttt Anturaqnini-ino... im. Direct Viniutfi. 51325 lioxazint llo.

In general. it is desirable for the energy absorbent printing formulation, when dried, to have relatively 10W reflection factors in the `ptiivelcngth range from about 0.38 to about 1.20 microns, for example, below about 20 percent, and preferably below about I() percent.

'I'lie following examples are illustrative of the invention, while notbcing intended to be limitative thereof:

.t EXAMPLE 1 A polyacrylic fabric is dyed with a single fluorescent dye, Basic Blue 4 (Color Index Number 51004), by placing the fabric in a dye bath at 120 F. containing the following composition based on the weight of the fabric:

Percent Basic Blue 4 t'tn'cd b v Rohm & l-laas Company) 1.0 Organic cationic retarder t'Rctarder LAN," manufactored by E. I. du Pont de Nemours & Co.,

Inc.`) 1.0

Demineralized water 95.8

The dye bath, which has a pH of about 5.0, is raised to its boiling temperature over a period of about 45 minutes. Boiling is continued for up to 2 hours or until the color is substantially removed from the dye bath; The fabric is rcmovcdfrom the dye bath and rinsed in deri'iineralized water and-dried.

Cyanamid Company) 20.0 Sodium alginate L 5.0 Water 95.0

The printed fabric is dried and the dried, printed, previously dyed fabric is analyzed on its printed surface with a Beckman .DU Quartz Spectrophotometer using a xenon lamp as a source of white light to determine its reflection factors, as defined above and in accordance with the method described above. The results are shown in FIG. l in middle curve B, designated Printed Shade.

For comparative purposes, a piece of the dyed fabric lafter drying thereof but without any printed lines applied thereto is analyzed in a similar manner forref'lection factor, the results thereof being shown in lFIG. 1 in the upper curve A, designated Ground Shade. Also, a similar polyacrylic fabric in undyed formftdtis printed solidly, rather than in the formof lines, over large enough area to enable analyzing the solid black surface for reflection factor` and analyzed in a similar mannerl to that employed with the printed fabric and the Ground Shade (dyed only) fabric. The resultsare shown in the lowermost C curve, designated Black.

It is apparent from FIG. l that thc dyed and printed fabric produced in accordance with this example has a lower reflection factor throughout the range of the spectrum analyzed,` namely at wavelengths of 0.5 to 1.0 micron, than the dyed only fabric; in other Words, Printed Shade curve Bis lower than Ground Shade curve A. The significant aspect of this example is that the Printed Shade sample retains a fairly high reflection factor in the wavelength range from 0.70 to 0.90 micron whileI the reflection factor in the wavelength range above 0.90 micron has been greatly reduced, thus rendering thc lrinted Shade fabric difficult to detect either by infrared photography or by means of a sniperscope. And the alternate black lines and blue separations would be quite difficult to distinguish visually at viewing distances of 50 meters or more against a lmckground with which the blue ground shade would blend well.

The foregoing example illustrates the principle of the method of the invention without reference to use in connection with camouflage in the visible range of the spectrum .under` field conditions.

nxAMPi ,n 2

A pol \f'ncr1ylic fabric is dyed with a combination nf- *llc* l.\" tlib'tltt. tbc fabric in a d vc bath ut 120" l-` taining thc following composition of thc fabric:

. CUM* based on the weight Non-ionic surfactant (Triton X-'l()0, manufaclurcd by Rohm llaas Company) 1.0 (.)rganic cationic retarder ("Rctardcr LAN." inanufacturcd by l'. I gdu lont de Nemours & Company` lne.) l.(l Deinineralized water 94.86

the dye bath. which has a pll of about 5.0, is raised to its boiling tempcraturcover a period of about 45 minutes. Boiling is continued for up lo 2 hours or until the color is removed from the dye hath. v'llie fabric is removed from the dye batlr' and rinsed in dcmineralized water and dried.

The dried, dyed fabric is silk-screen printed in the same manner as that described in Example t. The printed fabric is analyzed with a Beckman DU Quartz Spectrophotometer in the same manner as the dyed and printed fabric of Example l. The dyed. but imprinted, fabric was also analyzed as in Example l. The results are shown in FIG'. 2, the reflection factor of the dyed andprinted fabric at various wavelengths being shown in the middle curve B, designated Printed Shade, while the reflection factors of the dyed, unprinted fabric at various wavelengths are shown in the upper curve A, designated Ground Shade. The lowermost curve C, designated Black, is similar to that in FIG. t and is obtained in the same manner as described in Example l. FIG. 3 illustrates the surface appcaranceof the dyed and printed fabric. The fabric is generally represented by the numeral 1, the printed lines by the numeral 2. and the dyed portions of fabric betwecnthe printed lines by t'he numeral 3.

It is apparent that the presence of non-fluorescent dyes in combination with' a fluorescent dye in the Adye bath does not subst-antially interfere with the behavior of the fluorescent dye in the infrared portion of the spectrum. Also, it is apparent that the printed black energy absorbent lilies act in substantially the same manner when the ground shade includes a `mixture of dyes as when it contains only one dye. The dyed' and printed fabric of this exi-imple exhibits good camouflage characteristics both in daylight and at night since it retains effectively high fluorescence in the near infrared range, while its reflection factor in the far infrared is not so high as to be easily detectable with a snipcrseope, and the blackllines and lighter colored separations in the visible range blend sufficiently in daylight or artificial light at distances of l() meters or less to prevent easy visual distinguishing of the fabric from a green background.

- 7 IurfAh'llLl", 3 An acrylic fabric is dyed as in llxample 2. except that tbe dye bath has the following dye formulation based on the weight ofthe fabric:

Percent Basic Blpe 4 (CI. No. 51004) 0.35 fllasic Yellow l5 1.15

Basic Red 14 0.18 Sodium,I acetate 1.0 Acctic acid (56%) 1.0

Non-ionic surfactant (Triton X-l00," manufactured by Rohm & Haas Company) 1.0 Organic cationic retarder (.Retarder LAN, manufactured by F.. I. du Pont de Nemours & Company, Inc.) 1.0 Iemineraliyed water 11.34

'lhe resultant Ground Shade approximately matches Olive Grcen'* 106 when viewed under a standard shade lamp operating at a correlated -color temperature of 7500" li.

The dyed fabric is silk-screen printed in the same manner as in lxamples l and 2. 'except using a printing formulation having the following composition:

, Grams Carbon black dispersion 10.0 Iron oxide yellow i.y 50.0

Acrylic padding emulsion (She`rdye Padding Emul- This printing formulation produces lines of an olive drab shade which blend well with the olive green Ground Shade in the visible range of the spectrum. As seen in FIG. 4,

the rellectionvfactor curve for the dyed fabric is shown in curve A, and the rcllcction` factor curve for the dyed and printed fabric in curve B," Curve C is determined in the same manner as curve C' of PIG. 1. The dyed and `printed fabric (curve B) shows behavior in the infrared range of the spectrum similarl to that of the dyed and printedfabric of Example 2, although the reflection factor curve for the printed on printing formulation (curve C) is appreciably higher in the infrared than the reflection factor curves for the black carbon pigment onlyin FIGS.

1 and 2. The dyed and printed fabric of this example provides good camouflage against infrared photography in the near infrared range, against detection with a sniperscope using the far infrared range, and against visual observation even close up in an environment with which olive green shades would blend well because the printed on lines blend well with the ground .shade separations,

providing an almost true solid shade throughout the fabric surface.

EXAMPLE 4 Using the same two coloring formulations as ,lxam ple 3, a polyacrylic fabric is first screenprinted'hvith the printing formulation with one-sixteenth inch wide lines separated one-sixteenth inch apart and thereafter dyed with the dye formulation. The reflection factor curves for the resulting fabric are shown in FIG. 5, curve B representing the printed and dyed fabric, curve A representing the same fabric dyed only with the dyc formulation, and curve C representing the dried printing formulation, this curve being determined in the same manner as curve C of FIG. l. It is apparent that the printed and thereafter dyed fabric shows substantially the same reflectance characteristics in the infraredA as the fabric which is first dyed and thereafter printed, as in Example 3. Also, because of the close similarity of the olive green shades of the dyed portions and the printed portions of the fabric, the printed and dyed fabric presents a substantially solid shade appearance in the visible range of thc spectrum and is u'ell eamoullagcd in an environment which blendsv well with olive green and furthermore is not easily dctectcd by infrared photography using the near infrared or by means of the sniperscope using thc far infrared portion of the spectrum. lt is apparent, therefore, that the printing on of the black energy absorbing pigment in the printing formulation may be done prior to dyeing as well as subsequent to dyeing of the fabric in the separations between the lines of energy absorbing pigment with substantially equally effective camouflage results.

Although in the above examples carbon served as the black energy absoibnt pigment compo-font of the printing formulations` it is to be understood that other highly energy absorbent pigments may be similarly employed. For example. black iron oxide may be used and is quite cll'cctirc. lhcte are numerous other black or wry dark pigments which may be similarly uscd,vprovided they do not havt` a tendency to degrade tht` substrate material. lixamples of other such pigments are certain black metal oxides` such as tin oxide, cupric oxide, lead oxide, silver oxide` cobalt oxidevanadium oxide, ehromiunroxit'le, germanium oxide, and molybdenum oxide, certain black metal sulpbidcs. such as cuprous sulphide` cupric sulphide, lead sulphide, silver sulphide, cobalt sulphide. molybdevnum `sulphide, nickel sulphide, vanadium sulphide, and

many, other black or very dark crystalline or amorphous substz'rnecs. Ilcmcnta'l silicon may also be used as the energy absorbent pigment.

ln the above examples. acrylic or polyaerylie fabrics were used as the 4substrate materials which were dyed and printed or first printed and then dyed in accordance with the invention. However, it is to be understood that the invention is applicable to ary substrate material which is dycable by dyes which lluorescc in the infrared region, especially in the near infrared, when used in combination with the selected substrate material. Furthermore. the substrate material may be in any suitable form for thc purpose it is designed to serve.

lt is also to be understood that the printed lines are not required to be perfectly straight to serve the camouflaging purposes of the invention. It may even be highly desirable in certain instances for the enhancement of camouflage against certain types of background to have the linesprinted in selected curved or wavy designs. The important consideration is toI produce'in a camouflaged article the maximum degree of blending in with the background environment in which the article is to be used, the blending -in being as nearly complete as possible over the range of wavelengths from about 0.38 to about 1.20 microns or even higher so that the article may be employed in the daylight or at night without being in scrious jeopardy of detection by visggal observation, by infrared photography, or"by sniperseope or other electrooptical means. This may even oe accomplished by dyeing and printing a fabric with ,a pattern of dots or in a checkerboard design or by other means of distributing the printed on portions of black pigment-containing cornposition relatively uniformly over the entire area of the material.

The method of the invention is very useful in producing camouflage effects on fabrics as well as other forms of is sensitive in the near infrared region from about 0.70 to about 0.90 micron in wavelength, or bymeans ofthe sniperscope at night, by irradiating the uniform with infrared energy of from about 0.90 to about 1.20 microns wavelength. Thus, a soldier wearing a uniform made in accordance with the present invention will have greatly impi'oved chanccsll'of not being detected by the enemy and, therefore, much improved chances of survival under combat conditions. When applied to tentage, the invention greatly reduces the chances of detection by an enemy of' positions where troops or equipment and supplies are sheltered, particularly by means of infrared aerial photography, thus reducing the losses of troops, equipment and supplies due to bombings'rof shelters.

We wish it to be understoodI that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

We claim:

1. Method of treating a dyeable material to minimize detection thereof by visual observation or by infrared detection means including infr fed photography and sniperscope means which comprisesthe steps of: "t (a) dyeing said material with a dye composition which imparts to said material tluorescencc in the wavelength range from about 0.70 to about 0.90 micron producing a reflection factor of at least about 35% for at least one wavelength of radiant energy in said wavelength range,

(b) drying Said material after said dyeing thereof,

(c) printing selected portions of said dyed and dried material with a printing composition which when dried has reflection factors below at least about 35% for radiant energy in the wavelcngthft'range from about 0.38 to about 1.20 microns, said selected portionsvbeing substantially uniformly distributed over the entire area of said material and being of a width of at least about 1/16 inch and being spaced at least about im; inch apart to provide a printed and dried material having reflection factors below about .35% for radiant energy at all wavelengths in the wavelength ranges from about 0.38 to about 0.70 micron and from about 0.90 to about 1.20 microns and a reflection factor not less than about 35% for radiant energy of at least one wavelength in the wavelength range from about 0.70 to about 0.90 micron, and

(d) drying Asaid printed material.

2. The method of claim 1 wherein said selected portions comprise substantially uniformly spaced lines of substantially uniform width.

` 3. The method of claim 2 wherein saidlines are about 1/16 in width and are spaced about 1/16 apart. y

4. The method of claim 1 wherein said printing 4composition comprises a radiant energy absorbent black pig- 5, The method ol" claim 4 wherein said pigment cornpriscs carbon.

6. The method of claim 1 wherein thc steps of printing said material and drying said printed material are carried out prior to the steps of dyeing said material and drying said dyed material.

7. A treated article having Selected portions of the surface of said article having reflection factors below about 35% for radiant energy at all wavelengths in the wavelength ranges from aboutf0.38 to about 0.70 micron and from about 0.90 to about 1.20 microns and the remainng portior; of the surface ol' said article having a reflection factoi` not less than about 35% for radiant energy of at least one wavelength in the wavelength range from about 0.70 toabout 0.90 micron, said selected portions being substantially uniformly distributed over the v surface ot` said article. whereby said article is etl'cctirely tions of said surface are dyed with a dye composition which imparts to said surface tinoresccnce in the wavelength range from about 0.70 to about 0.90 micron and having a high rellection factor `for radiant energy of at least one wavelength *in said wavelength range.

9. -A treated article according to claim 7 wherein said treated article is textile fabric.

It). A treated article according to-clairn 7, wherein said treated article is film.

Referhces cned FOREIGN PATENTS 9/1944 Great Britain 8-14 563,993 566,921 1/l945 Great Britain 8-14 1,264,654 3/1968 Germany 8-14 GEORGE F. LESMES, Primary Examiner H. WOLMAN, Assistant Examiner Us. c1. XR.

8 1 XA, I4, 17, 18, 62; 1l7--33.5 T, 33.5 R 

